CN114430867A

CN114430867A - Battery system with parallel connection protection

Info

Publication number: CN114430867A
Application number: CN202080066544.1A
Authority: CN
Inventors: 迈克尔·马歇尔; 雅各布·施迈茨
Original assignee: Briggs Stratton Ltd
Current assignee: Briggs Stratton Ltd
Priority date: 2019-08-28
Filing date: 2020-08-27
Publication date: 2022-05-03
Anticipated expiration: 2040-08-27
Also published as: US20220407122A1; CN114430867B; WO2021041684A1; EP4022705A4; EP4022705A1

Abstract

A battery includes a housing having a positive terminal and a negative terminal. A battery cell is located within the housing and is selectively coupled to the positive terminal and to the negative terminal. A battery management system is located within the housing and is configured to operate a first switch within the housing to selectively couple the battery cells and the positive terminal. A bleed circuit is electrically coupled between the positive terminal and the negative terminal. The bleed circuit includes a resistor and a second switch for selectively coupling the positive terminal to the negative terminal. The battery management system is configured to open the first switch and close the second switch, and measure a voltage drop across the resistor to detect the presence and type of voltage source connected to the positive terminal.

Description

Battery system with parallel connection protection

Cross Reference to Related Applications

This application claims priority from U.S. provisional patent application No. 62/892,803, filed on 28.8.2019, the contents of which are hereby incorporated by reference in their entirety.

Background

The present invention relates generally to the field of indoor and outdoor power equipment, and in particular to the field of battery powered indoor and outdoor power equipment.

Disclosure of Invention

At least one embodiment of the present disclosure is directed to a battery pack. The battery includes a housing having a positive terminal and a negative terminal. A battery cell is located within the housing and is selectively coupled to the positive terminal and to the negative terminal. A battery management system is located within the housing and is configured to operate a first switch within the housing to selectively couple the battery cells and the positive terminal. A bleed circuit is electrically coupled between the positive terminal and the negative terminal. The bleed circuit includes a resistor and a second switch for selectively coupling the positive terminal to the negative terminal. The battery management system is configured to open the first switch and close the second switch, and measure a voltage drop across the resistor to detect the presence and type of voltage source connected to the positive terminal.

Another embodiment of the present disclosure is directed to a battery pack. The battery includes a housing having a positive terminal and a negative terminal. A battery cell is located within the housing and is selectively coupled to the positive terminal and to the negative terminal. A battery management system is positioned within the housing and is configured to operate a main contactor switch and an auxiliary contactor switch to selectively couple the battery cells to the positive terminal. A bleed circuit extends between the positive terminal and the negative terminal. The bleed circuit includes a resistor and a bleed switch for selectively coupling the positive terminal to the negative terminal. The battery management system is configured to determine the presence of a voltage source on the positive terminal when the auxiliary contactor switch is in the open position. The battery management system is also configured to determine a type of the voltage source on the positive terminal when the auxiliary contactor switch is in a closed position and the bleed switch is in a closed position.

Another embodiment of the present disclosure is directed to a battery system. The battery system includes a first battery pack and a second battery pack each connected to a terminal bus. The first battery pack supplies a voltage to the terminal bus. The second battery pack includes a bleed circuit, one or more contactors, one or more battery cells, and a battery management system. The one or more battery cells are selectively coupled to the terminal bus based on a position of the one or more contactors. The battery management system is configured to measure the voltage of the terminal bus coupled to the bleed circuit, the voltage corresponding to an output voltage of the first battery pack. The battery management system is also configured to determine whether the voltage of the terminal bus is less than a predetermined value. In response to determining that the voltage is less than the predetermined value, the battery management system is configured to turn on the bleed circuit with the terminal bus to attempt to bleed the voltage of the terminal bus. In response to determining that the voltage of the terminal bus is not bleeding by the predetermined threshold amount, the battery management system determines whether the voltage of the terminal bus is within a lockout voltage range. If the battery management system determines that the voltage of the terminal bus is within the lockout voltage range, the battery management system couples the battery cell to the terminal bus by closing the one or more contactors.

Another embodiment of the present disclosure is directed to a battery system. The battery system includes a plurality of battery packs in a parallel configuration, and an individual battery pack. The standalone battery pack includes a bleed circuit, a primary contactor, an auxiliary contactor, one or more battery cells, and a battery management system. The battery management system is configured to measure a voltage of a terminal bus coupled to the bleed circuit and to measure a voltage between the main contactor and the auxiliary contactor. The battery management system is further configured to delay initiating a test of coupling the individual battery pack to the plurality of battery packs based on a preprogrammed value. The battery management system is further configured to turn on the bleed circuit of the individual battery pack to attempt to bleed the voltage of the terminal bus. In response to the voltage of the terminal bus bleeding by a threshold amount (as detected by the battery management system), the battery management system is configured to couple the individual battery pack to the plurality of battery packs.

Another embodiment of the present disclosure is directed to a method of coupling a battery pack in parallel to a common terminal bus. The method includes measuring a voltage of a terminal bus coupled to a bleed circuit of the individual battery pack. The standalone battery pack includes the bleed off circuit, one or more contactors, one or more battery cell assemblies, and a battery management system. The method also includes delaying the start of a test coupling the individual battery pack to the plurality of battery packs based on a predetermined value. The method also includes engaging the bleed circuit of the individual battery pack to attempt to bleed the voltage of the terminal bus. The method also includes coupling the individual battery pack to the plurality of battery packs in response to the voltage of the terminal bus bleeding by a threshold amount. The plurality of battery packs are arranged in a parallel configuration.

Drawings

The present disclosure will become more fully understood from the detailed description given below when taken in conjunction with the accompanying drawings, wherein:

fig. 1 is a schematic diagram of a battery system having battery packs connected in a parallel configuration according to an exemplary embodiment;

FIG. 2 is a schematic view of the battery system of FIG. 1 with the battery pack in an ideal nominal state;

FIG. 3 is a schematic view of the battery system of FIG. 1 with the battery pack in a non-ideal state;

FIG. 4 is a schematic diagram of the battery system of FIG. 1, in an additional case scenario in which the battery pack is in a non-ideal state;

FIG. 5 is a schematic diagram of the battery system of FIG. 1 with the battery pack in a non-ideal state and illustrating a parallel process;

fig. 6 is an internal schematic diagram of a battery pack and a bleed circuit for a parallel process in the battery system of fig. 1;

FIG. 7 is a view of a battery system of FIG. 1One isAn internal schematic of the battery pack showing a bleed circuit functional schematic;

fig. 8 is a flow diagram of a process for determining the ability of a battery pack to engage in parallel with other battery packs of the battery system of fig. 1 using the bleed off circuit discharge of fig. 7, according to some embodiments;

fig. 9 is a flow diagram of a process continuing from the process of fig. 8 for determining the ability of a battery pack to engage in parallel with other battery packs using the bleed circuit discharge of fig. 7, in accordance with some embodiments;

Fig. 10 is a sorting table used in a parallel process for discharging the battery system of fig. 1;

fig. 11 is an internal schematic view of one of the battery packs in the battery system of fig. 1, showing another embodiment of a bleed circuit functional schematic;

fig. 12 is a flow diagram of a process for determining the ability of a battery pack to engage in parallel with other battery packs of the battery system of fig. 1 using the bleed off circuit discharge of fig. 11, according to some embodiments;

fig. 13 is a flow diagram of a process continuing from the process of fig. 12 for determining an ability of a battery pack to engage in parallel with other battery packs of the battery system of fig. 1 using the bleed off circuit discharge of fig. 11, in accordance with some embodiments;

FIG. 14 is an example of a bleed circuit sequence timeline for discharging one of the battery packs in the battery system of FIG. 1;

fig. 15 is an example of a bleed circuit sequence for a parallel process for discharging one of the battery packs in the battery system of fig. 1, where there is only one battery and there is no terminal energy storage device;

fig. 16 is another example of a bleed circuit sequence for a parallel process for discharging one of the battery packs in the battery system of fig. 1, where there is only one battery and there is a terminal energy storage device;

Fig. 17 is another example of a bleed circuit sequence for a parallel process for discharging one of the battery packs in the battery system of fig. 1, where there is only one battery and there is a terminal energy storage device;

fig. 18 is an example of a bleed circuit sequence for a parallel process for discharging one of the battery packs in the battery system of fig. 1 in which there are two or more batteries and no CANbus communication;

fig. 19 is another example of a bleed circuit sequence for a parallel process for discharging one of the battery packs in the battery system of fig. 1, where there are two or more batteries and no CANbus communication;

FIG. 20 is a sorted list used in a parallel process for charging the battery system of FIG. 1;

fig. 21 is a flow diagram of a process for determining the ability of a battery pack to engage in parallel with other battery packs of the battery system of fig. 1 using the bleed circuit charging of fig. 7, according to some embodiments;

fig. 22 is a flow diagram of a process continuing from the process of fig. 21 for determining the ability of a battery pack to engage in parallel with other battery packs of the battery system of fig. 1 using the bleed circuit charging of fig. 7, in accordance with some embodiments;

Fig. 23 is a flow diagram of a process for determining the ability of a battery pack to engage in parallel with other battery packs of the battery system of fig. 1 using the bleed circuit charging of fig. 11, according to some embodiments; and is

Fig. 24 is a flow diagram of a process continuing from the process of fig. 23 for determining the ability of a battery pack to engage in parallel with other battery packs of the battery system of fig. 1 using the bleed circuit charging of fig. 11, in accordance with some embodiments.

Detailed Description

Before turning to the figures, which illustrate exemplary embodiments in detail, it is to be understood that the application is not limited to the details or methodology set forth in the description or illustrated in the figures. It is also to be understood that the terminology is for the purpose of description and should not be regarded as limiting.

Referring generally to the drawings, the battery system described herein allows multiple battery packs to be arranged in a parallel configuration such that significant inrush or blocking current is avoided regardless of whether the battery packs are currently in the same state of charge or the same output voltage. Conventional batteries (e.g., lithium-ion type, lead-acid type) connected in parallel to a common terminal bus attempt to immediately balance the state of charge between the batteries on the bus. Very high currents may be experienced if the state of charge difference between the batteries is significant. Lead acid batteries have a very high internal resistance and are better able to withstand charge balancing because the current seen by the battery is much lower due to ohm's law. However, because lithium-ion batteries traditionally have much lower internal resistances than lead-acid batteries, lithium-ion batteries are less equipped to handle state of charge imbalances. In some cases, the difference in state of charge between cells along the common terminal bus may result in currents of 3000A or higher within the lithium ion battery, which may cause significant damage to the cells themselves. The disclosed battery system is designed such that: by monitoring the terminal bus and connecting the terminal bus only if the battery pack has determined that the connection terminal bus is safe, the battery pack and devices are protected from experiencing these large inrush or latching currents that may be detrimental to the health of the battery pack, equipment, and the entire battery system.

The battery packs within the battery system are designed such that each battery pack can detect the presence and type of device connected to the terminal bus before engaging the battery cells within the battery pack to the common terminal bus. To monitor the terminal bus, the battery pack includes a battery management system that monitors the voltage and/or current along the terminal bus. The battery management system operates and monitors bleed off circuitry within the battery pack to detect the presence of charging along the terminal bus. Initially, the battery management system determines whether voltage is present on the terminal bus. If the battery management system does not detect a voltage along the terminal bus, the battery management system allows the battery pack (e.g., the battery cells within the battery pack) to engage the terminal bus because there is no risk of detecting an over-current condition. If the battery management system does detect a voltage along the terminal bus, the battery management system will attempt to identify the type of power source providing the voltage on the terminal bus. To identify the voltage source type, the battery management system connects the terminal bus to a bleed circuit within the battery pack and monitors a voltage drop across the bleed circuit over a period of time. If the detected voltage source is provided by the equipment itself (e.g., by a capacitor on the motor of the stored energy power equipment, etc.), then the voltage detected by the battery management system will decrease over time as the terminal bus is effectively "erased" any charge. The current passes through the terminal bus to the bleed circuit and then to ground as the energy source dissipates. Considering the exponential decay nature of the capacitive energy source, the battery management system determines that there are no other batteries on the terminal bus based on the rate of change of the detected voltage across the bleed circuit. Thus, the battery management system again determines that the battery engagement terminal bus is safe and coordinates the internal switches to establish electrical connection between the battery cells within the battery pack and the terminal bus.

If the battery management system does not detect that the voltage source is depleted over time, the battery management system knows that the voltage source may be another battery. The battery management system then measures the voltage on the terminal bus using the bleed off circuit and associated sensors. If the difference between the voltage on the terminal bus and the voltage within the battery pack is within a predetermined range (e.g., +/-1.00V), the battery management system will determine that it is also safe for the battery to engage the terminal bus, since the difference between the voltage within the battery pack and the voltage along the terminal bus will not cause significant inrush or blocking currents that could damage the battery pack. The battery management system will again coordinate internal switches to couple the battery cells to the terminal bus to allow the battery pack to discharge through the terminal bus. Each battery within the battery system may include a battery management system to monitor the charge on the terminal bus to determine whether it is safe for the battery to engage the terminal bus and release energy, so that the battery engagement process may occur sequentially when all batteries are at approximately equal states of charge.

The battery system (e.g., a battery management system within the battery pack) will also prevent the battery from engaging the terminal bus if an unsafe condition is detected. For example, if the battery management system detects the presence of another battery along the terminal bus (e.g., indicating a capacitive energy source because the voltage is not draining over time), the battery management system detects the battery voltage within the battery pack and compares it to the voltage along the terminal bus. If the difference between the two exceeds a predetermined range (e.g., +/-1.00V), the battery management system will know that bonding the battery cells to the terminal bus may cause damage to the battery pack. Thus, the battery management system will cause the internal switches to open to prevent communication between the battery cells and the terminal bus. The battery management system will continue to monitor the voltage along the terminal bus until it is eventually detected that (1) there is no further voltage source along the terminal bus or (2) the voltage source along the terminal bus is within a predetermined allowable range, and it is now safe to engage the terminal bus in a parallel configuration. Using the battery system described herein, the battery pack avoids potentially damaging currents that may be caused by the batteries blindly engaging the terminal bus in a parallel arrangement, regardless of whether there are other voltage sources along the terminal bus.

Parallel battery pack configurations are commonly used in battery packs for various types of indoor and outdoor power equipment, as well as for portable worksite equipment and military vehicle applications. Outdoor power equipment includes mowers, riding tractors, snow throwers, pressure washers, tillers, log splitters, zero turn radius mowers, rear-steer mowers, riding mowers, upright mowers, pavement surface treatment equipment, industrial vehicles such as forklifts, utility vehicles, commercial lawn equipment such as blowers, vacuum cleaners, debris loaders, seeders, leaf trimmers, aerators, turf cutters, brush mowers, portable generators, and the like. Indoor power equipment includes ground grinders, ground dampers and polishers, vacuum cleaners, and the like. Portable worksite equipment includes portable lighting lamps, mobile industrial heaters, and portable lamp holders. Military vehicle applications include installing battery systems on All Terrain Vehicle (ATV), utility mission vehicle (UTV), and Light Electric Vehicle (LEV) applications. The parallel arrangement of the battery packs is particularly useful and common in situations where the battery packs do not have predetermined or designated equipment. The ability to determine the presence of other voltage sources along the terminal bus becomes particularly useful because the same battery pack can be used to power several different power equipment.

Referring to fig. 1, a battery system 100 is shown with battery packs connected in a parallel configuration, according to an exemplary embodiment. The battery system 100 may have up to four different battery packs 102, 104, 106, 108 connected together in parallel, with each positive terminal of the battery packs 102, 104, 106, 108 connected to a positive terminal bus 122 and each negative terminal of the battery packs 102, 104, 106, 108 connected to a negative terminal bus 124. Various battery arrangements may also be used. For example, the battery system 100 may have only a single battery pack 102, or may have the battery pack 104, the battery pack 106, and the battery pack 108 connected in a parallel configuration. The battery system 100 may have more than four different battery packs connected in parallel, such as sixteen or more battery packs. Negative terminal bus 124 is connected to a common ground so that battery pack 102, battery pack 104, battery pack 106, and battery pack 108 are all grounded together. In some embodiments, the battery pack 102 and other battery packs in the system 100 are lithium ion batteries. In other embodiments, the battery pack 102 and the other battery packs in the system 100 are different battery types (e.g., lead acid type, lithium polymer type, nickel cadmium type, etc.).

In a typical case, each

battery pack

102, 104, 106, 108 in the battery system 100 is connected to a 29 bit controller area network bus (CANbus) network for sending and receiving communications from other battery packs. The CANbus link 110, the CANbus link 112, and the CANbus link 114 are complete to allow network communications between the battery packs 102, 104, 106, 108 of the battery system 100. Alternatively, other digital communication protocols may be used instead of CANbus communication. For example, the digital communication protocol may use one or more of I2C, I2S, serial, SPI, Ethernet, 1-Wire (single bus), and the like. In addition, each

battery pack

102, 104, 106, 108 in the battery system 100 may be connected to the same charge enable signal and the same discharge enable signal as each of the other battery packs. For example, the discharge enable signal 116 is connected to the discharge enable signal 118 and the discharge enable signal 120.

Referring to fig. 2, a battery system 200 is shown with battery packs in an ideal nominal state connected in a parallel configuration as described with reference to fig. 1, according to an exemplary embodiment. In an ideal situation, each battery pack in the battery system 200 is charged to the same amount, and thus has the same state of charge (SOC). For example, battery pack 202, battery pack 204, battery pack 206, and battery pack 208 each have a state of charge of 75% of full charge capacity. Further, in this state, each battery pack in the battery system 200 is also connected to a CANbus network (e.g., a CANbus link 210, a CANbus link 212, and a CANbus link 214 are operating normally). Battery pack 202 may then communicate with battery pack 204, battery pack 206, and battery pack 208 via a CANbus network. The communication may include, for example, messages related to the charging of the battery pack 202 or the health of the battery cells within the battery pack 202. Additionally, in the nominal state, the battery system 200 is configured such that each

battery pack

202, 204, 206, 208 receives a charge or discharge enable signal (via discharge enable

signals

216, 218, 220), respectively, at the same time as the other battery packs in the battery system 200. Similar to the battery system 100, the battery system 200 shows each

battery pack

202, 204, 206, 208 electrically coupled to each of a positive terminal bus 222 and a negative terminal bus 224.

Referring to fig. 3, a battery system 300 is shown having a battery pack 302, a battery pack 304, a battery pack 306, and a battery pack 308 connected in a parallel configuration. Unlike the battery system 100 shown and described in fig. 1, the battery system 300 is shown in a non-ideal state. Non-ideal system conditions will occur when any or all of the following occurs: the battery packs 302, 304, 306, 308 within the battery system 300 possess a unique state of charge as compared to any of the other battery packs; one or more of the battery packs 302, 304, 306, 308 are disconnected from the 29-bit CANbus network; and/or any of the battery packs 302, 304, 306, 308 receive respective charge or discharge enable signals at a separate time from any of the other battery packs 302, 304, 306, 308. For example, if the discharge enable signal 316 for battery pack 302 experiences a communication error and is not operating properly, or if the CANbus link 314 is down and no messages are received or sent across link 314, then battery system 300 is in a non-ideal state. Battery systems with any of these conditions are undesirable due to problems caused by having non-ideal system conditions. For example, when the discharge enable

signals

316, 318, 320 are not operating properly, different rates of discharge may occur between the battery packs 302, 304, 306, 308 and the positive terminal bus 322 or the negative terminal bus 324 to which each

battery pack

302, 304, 306, 308 is coupled.

The non-ideal state of charge with a unique state of charge prevents two or more battery packs from engaging the positive terminal bus at the same time because different states of charge can produce extremely high blocking currents. If the latching current is not reduced or eliminated, the latching current may cause damage to the health of the battery pack. If a

battery pack

302, 304, 306, 308 within the battery system 300 is disconnected from the CANbus network and does not receive communications from other battery packs 302, 304, 306, 308, the battery pack may not recognize the presence of other battery packs 302, 304, 306, 308 within the battery system 300 and may discharge differently. In conventional systems, if a disconnected battery pack attempts to engage a positive terminal bus (e.g., positive terminal bus 322) to which other battery packs are connected, a very high and potentially damaging blocking current may result from the attempt to connect positive terminal bus 322. Further, if the battery pack (e.g., battery pack 302) receives a charge or discharge enable signal at a different time than any of the other battery packs (e.g., battery pack 304, battery pack 306, and/or battery pack 308), battery pack 302 may attempt to engage positive terminal bus 322 while the other battery packs are connected. Similarly, if any two or more battery packs receive an enable signal to engage at exactly the same time, an attempt to engage the positive terminal bus 322 may result in a very high latching current, which may damage both battery packs.

Referring now to fig. 4, a battery system 400 is shown with a battery pack 402, a battery pack 404, a battery pack 406, and a battery pack 408 in a parallel configuration, which presents another non-ideal case scenario system state. In this case, the battery packs 402, 404, 406, 408 in the battery system 400 each have an SOC that is significantly different from the other SOCs, each battery pack is disconnected from the CANbus communication network, and each

battery pack

402, 404, 406, 408 receives a discharge enable signal at exactly the same time as the other battery packs. Fig. 4 shows that this scenario occurs when battery pack 402 has an 80% SOC, battery pack 404 has a 40% SOC, battery pack 406 has a 10% SOC, and battery pack 408 has a 90% SOC, CANbus link 410, CANbus link 412, and CANbus link 414 all experience complications and are inoperative, and discharge enable signal 416, discharge enable signal 418, and discharge enable signal 420 all occur at exactly the same time.

Fig. 5 shows the parallel process during the discharge mode, which may resolve a non-ideal battery pack. Similar to fig. 4, the battery system 500 is shown with all battery packs 502, 504, 506, 508 in a non-ideal state. This parallel process attempts to correct for non-idealities during the discharge mode, where the battery 508 attempts to engage the other battery packs 502, 504, 506. During this process, two different hardware-based processes may occur with the battery system 500 in a non-ideal state. First, a battery pack (e.g., battery pack 508) in battery system 500 may determine whether positive terminal bus 510 has any other energy storage device connected thereto, such as another

battery pack

502, 504, 506, a capacitor, or a capacitor "pack" (i.e., multiple capacitors in series and/or parallel). Then, if another

battery pack

502, 504, 506 is connected to the positive terminal bus 510, the battery pack 508 in the battery system 500 may determine whether it is safe to engage the positive terminal bus 510. Each battery management system having battery packs 502, 504, 506, 508 will perform to protect its own battery cells and to protect the components of the battery packs (e.g., wire bonds, wiring, contactors, etc. within the battery packs), with the overall ultimate goal of each battery pack being to supply power to a machine (e.g., outdoor power equipment, indoor power equipment, portable worksite equipment, military vehicle applications, etc.) in a safe manner.

Referring now to fig. 6, an internal view of a battery pack 600 and a bleed circuit for performing the parallel process of fig. 5 is shown. In some embodiments, battery pack 600 includes a main contactor 602, an auxiliary contactor 604, a bleed off circuit 608, a Battery Management System (BMS) 614, and a battery cell 618. The main contactor 602 and the auxiliary contactor 604 are electrical switches (e.g., MOSFETs, solid state relays, transistors, etc.) that may be turned on to connect with a positive terminal bus, such as the positive terminal bus 618. In some embodiments, the load 606 is electrically coupled between the positive terminal bus 618 and the negative terminal bus 620. The load 606 may be a machine to which the BMS 614 supplies power, such as a motor of an outdoor power plant. The bleed circuit 608 may be connected from the positive terminal bus 618 to a common ground at the negative terminal bus 620, as described with reference to fig. 1. The bleed circuitry 608 may be designed to include a load 610 and a solid state relay or bleed switch 612. The load 610 may be a load "bank" that includes other components, or may be a bleeder resistor that has a dual purpose as a heating element for a battery internal heater mat (not shown) used in a cold-resistant battery bank. In other embodiments, bleed circuit 608 includes other mechanical components to include a load that is connectable to BMS 614, positive terminal bus 618, and a ground at negative terminal bus 620.

The bleed circuit 608 may determine whether the positive terminal bus 618 is connected to another energy storage device (e.g., another battery pack or a capacitor). Inside the battery pack 600 at the BMS 614 level, the operation of the bleed circuit 608 initially is the switching device (e.g., the solid state relay 612) attempting to "bleed" the voltage at the positive terminal bus 618 (if present) through the load 610 to ground at the negative terminal 622. Bleeder circuit 608 then monitors how fast the voltage decays. For example, if the voltage at the positive terminal bus 618 is 40V and the bleeder circuit 608 finds the voltage to drop to 30V, there is a 25% change in the voltage from the bleeder circuit 608. If the voltage decay rate observed by the bleed circuit 608 is very high (e.g., 90% or higher), a capacitive energy storage device may be present and it is safe to engage the battery pack 600 in parallel to the battery system (e.g.,

battery systems

100, 200, 300, 400). However, if the voltage decay rate is very low (e.g., below 10%), meaning there is no or very little change in the terminal bus voltage across the bleed circuit 608, another battery pack or energy storage device (e.g., a 12V lead-acid battery or unauthorized charger) is connected to the positive terminal bus 618 and it may not be safe to join the battery pack 608 in parallel to the existing battery system.

Referring to fig. 7, a functional schematic 700 of the bleed circuit 608 in the battery pack 600 is shown. BMS 714 (which may be similar to BMS 614) may be connected to positive terminal bus 618 through main (terminal) voltage sensing 704. Future outputs 710 from BMS 714 may be connected to solid state relays 708 (e.g., Field Effect Transistors (FETs), transistors, Insulated Gate Bipolar Transistors (IGBTs), etc.) and positive terminal bus 618 through bleed-off resistor 706. The bleed circuit 608 may bleed the voltage at the positive terminal bus 618 to a common ground at the negative terminal bus 620 through the bleed resistor 706 and the solid state relay 708. In some embodiments, the bleeder resistor 706 has a resistance value of 10 ohms. BMS 714 can be connected to an internal battery current sensor 712 that is connected to the negative terminal bus 620 to be grounded. Internal battery current sensor 712 may be, for example, a shunt resistor. The battery cells 716 may be connected to the main contactor 702 at their respective positive terminals, to the common ground at the negative terminal bus 620 at their respective negative terminals, and to the BMS 714 so that the battery management system knows the status of the battery cells 716. The main contactor 702, when closed, connects the battery cells 716 to the positive terminal bus 618. In other embodiments, the battery pack 600 further includes a pre-charge relay (e.g., pre-charge relay 1128 shown in fig. 11) that, in addition to the function of the bleed circuit 608, may also help protect the main contactor 702 (or the main contactor 1102). The pre-charge relay may slow the voltage change over time to help prevent inrush currents that may damage battery pack components.

Referring to fig. 8, an automated process 800 is shown for determining the ability of a battery pack (e.g., battery pack 102) to be engaged in parallel with other battery packs (e.g., battery packs 104, 106, 108) of a battery system (e.g.,

battery systems

100, 200, 300, 400, etc.) using a bleed circuit (e.g., bleed circuit 608) discharge. Process 800 may be performed in part by an application associated with BMS 714. This process 800 may be used to prevent damage to the battery packs due to high inrush currents (e.g., 3000 amps of current) when joining battery systems having a parallel configuration. Process 800 begins with step 802, which performs a CAN source address request procedure to determine if there are other batteries on the CAN bus network. Step 802 may occur at some predetermined time (such as 1.5 seconds) from the input of the discharge enable signal. The predetermined time from the input of the discharge enable signal may be the exact same amount of time regardless of whether any other battery is found to be present. The presence or absence of any other CAN-enabled battery is logged and potentially performed by the battery system (e.g., if other batteries are found, digital communication may override the hardware-level parallel scheme and the battery may immediately engage the terminals). Next, at step 804, process 800 includes measuring a main contactor 702 voltage sense potential, which corresponds to the terminal bus voltage. Then at step 806, the BMS 714 determines whether the measured voltage is greater than or less than a predetermined value. If BMS 714 finds that the voltage is greater than the predetermined value, BMS 714 waits for a predetermined time and then re-measures the voltage at step 808. Next, at step 810, BMS 714 determines whether the newly re-measured voltage is now less than a predetermined value.

If the new voltage value is still too high, at step 818, BMS 714 issues a soft fault. For example, if the predetermined value is 60V and the value re-measured after waiting 10 seconds from the first measurement is still greater than 60V, BMS 714 may issue a soft fault indicating that a "high terminal bus voltage" is present.

Alternatively, if the voltage is found to be less than the predetermined value in step 806, the process 800 defers the time based on the measured battery voltage according to the discharge schedule at step 812. After the delay time from step 812, the BMS turns on the bleed off circuit (e.g., the bleed off circuit 608) and measures the percentage change in the terminal bus voltage at step 814. Once the change in the terminal bus voltage is measured, the process 800 ends at step 816. In the event that process 800 ends, process 900 may begin, as shown in FIG. 9.

Referring to fig. 9, a process 900 for determining the ability of a battery pack to engage in parallel with other battery packs using bleed off circuit discharge is shown, according to an exemplary embodiment. Process 900 may begin at the end of process 800 (e.g., beginning at block 816). In some embodiments, process 900 begins at step 902, i.e., BMS 714 determines whether the percentage change in the terminal bus voltage after the bleed circuit 608 "bleeds" the voltage is greater than a predetermined value. If BMS 714 detects that the percentage change is greater than a predetermined value (e.g., greater than 90%), process 900 proceeds to step 904 where the battery pack engages the terminal bus (by engaging the main contactors) and changes the mode to "discharge". For example, if the percentage change is greater than 15% within 100 milliseconds (ms), the main contactor 702 turns on and the battery pack 600 engages the positive terminal bus 122 and enters a "discharge" mode.

Conversely, if BMS 714 detects in step 902 that the percentage change is less than the predetermined value, process 900 continues to step 906, where BMS 714 causes the bleeding circuit to continue operating for an additional predetermined time. In some embodiments, the predetermined value is 15% within 100 ms, and the additional predetermined time for which the bleeding circuit operation continues is 50 ms, giving a total amount of time of 150 ms.

After the additional predetermined time has elapsed, the BMS 714 may again determine whether the percentage change is now greater than the predetermined value at step 908. If after the additional time, the percentage change is high enough, the process 900 proceeds to block 904 and the battery pack engages the terminal bus. If the percentage change is not high enough after step 906, process 900 proceeds to determine if the battery pack is within the lockout voltage at step 910. If the battery pack is not within the lockout voltage, BMS 714 changes the mode of the battery pack to "standby discharge" in the communication mode at step 912. However, if the battery pack is within the lockout voltage, process 900 proceeds to step 914, where the battery pack engages the terminal bus. For example, if the battery pack 600 is within the lockout voltage (e.g., as determined by BMS 714), the main contactor 702 turns on and the battery pack 600 engages the positive terminal bus 122 because another battery is present and within the lockout range.

Fig. 10 shows a discharge sequencing table 1000 that may be used in a parallel process of the battery system 100, such as the process 800 described with reference to fig. 8. In some embodiments, the discharge rank table 1000 includes a low voltage region 1002, a voltage range column 1006, a delay column 1004, and a sequence number column 1008. The low voltage region 1102 highlights voltage ranges that fall below the required minimum activation (actuation) threshold voltage (e.g., below 41.8V). The voltage range column 1006 may be used during step 812 in the process 800 to find the delay (in ms) corresponding to the measured terminal bus voltage value. For the discharge sort table 1000, the standard lockout voltage is set to +/-1.00V, and the next sequential incremental delay time is increased by 250 ms. In some embodiments, a blind (CANbus-free communication network) hardware parallel system has three battery packs already joined (i.e., latched) together when the fourth battery pack attempts to engage. For this example, a differential voltage of 1.00V may result in a transient balancing current of 40A, which is still safe to experience for the engaged battery pack.

Referring to fig. 11, another battery pack 1100 that may be used with the battery system 100 is shown. The battery pack 1100 includes a BMS 1118 that can be connected to a positive terminal bus 1124 via main (i.e., terminal) voltage sensing 1106. BMS 1118 may be connected between main contactor 1104 and auxiliary contactor 1102 through auxiliary voltage sensing 1114. The secondary voltage sense 1114 may be pulled internally to ground via a high resistance resistor to avoid a hold voltage in the circuit. Bleed signal 1116 may be connected to switching device 1110, which is grounded to a common ground at negative terminal 1126. In some embodiments, the bleed signal 1116 is connected to the switching device 1110 through the bleed resistor 1108 and between the secondary contactor 1102 and the primary contactor 1104. The bleed off resistor 1108 may have a resistance in the range of 1 to 100 ohms (e.g., resistor 1108 is a 20 ohm resistor). BMS 1118 may be connected to an internal battery current sensor 1120, which is then connected to ground through negative terminal bus 124, and may be similar or identical in resistance to internal battery current sensor 712 described with reference to fig. 7. Internal battery pack current sensor 1120 may be a shunt resistor, or may be another type of sensor (e.g., a hall effect sensor) in place of a shunt resistor. The machine (i.e., load) 1112 may be a variety of devices, such as a controller for outdoor power equipment, indoor power equipment, portable worksite equipment, military vehicle applications, or the like. The battery cells 1122 may be connected to the auxiliary contactor 1102 at their respective positive terminals, to the common ground at the negative terminal bus 1126 at their respective negative terminals, and to the BMS 1118 such that the battery management system knows the status of the battery cells 1122 within the battery pack 600. When both the auxiliary contactor and the primary contactor are on, the battery cells 1122 may be connected to the positive terminal bus 1124. As described above, the battery pack 1100 may include a pre-charge relay 1128 positioned in series with the battery cell 1122, the bleeder switch device 1110, the internal battery pack current sensor 1120, and the negative terminal of the battery cell (which may be coupled to the negative terminal bus 1126).

Referring to fig. 12, an automated process 1200 for determining the ability of a battery pack to engage in parallel with other battery packs using bleed off circuit discharge is illustrated. Process 1200 is shown as including performing a CAN source address request process at step 1202 to determine if there are other batteries on the CANbus network. Step 1202 may occur a predetermined time (such as 1.5 seconds) from the discharge enable signal input, which may be the exact same amount of time regardless of whether any other batteries are found to be present. The presence or absence of any other CAN-enabled batteries is recorded (e.g., by BMS 1118). At step 1204, a voltage sensing potential (i.e., terminal bus voltage) of the main contactor 1104 is measured (e.g., by BMS 1118). In some embodiments, at step 1206, the BMS 1118 determines whether the measured voltage is greater than or less than a predetermined value. If the voltage is found to be greater than the predetermined value in step 1206, the BMS 1118 proceeds to step 1210 and waits for a predetermined time before restarting the process to re-measure the voltage.

After waiting the predetermined period of time, the BMS 1118 determines whether the newly re-measured voltage is now less than the predetermined value at step 1222. If the new voltage value is still greater, a soft fault is issued at step 1224. For example, if the predetermined value is 60V or greater than 60V, and the re-measured value is still greater than 60V after waiting 10 seconds and restarting the process, the BMS 1118 may issue a soft fault indicating that a "high terminal bus voltage" is present. Conversely, if the voltage is found to be less than the predetermined value in step 1206, process 1200 proceeds to step 1208, where BMS 1118 measures the secondary (contactor) voltage sensing potential. At step 1212, the BMS 1118 checks whether the measured auxiliary voltage is zero, which may indicate that there is a problem with the main contactor. If the auxiliary voltage is not 0V, BMS 1118 issues a soft fault in step 1224 indicating that there may be a main contactor fault.

However, if the secondary voltage is 0V, the process 1200 continues to step 1214, where the BMS 1118 turns on the bleed off circuit (e.g., the bleed off circuit 608) and measures the current of the battery pack for a predetermined period of time. After measuring the battery current, the BMS 1118 determines whether the current exceeds a predetermined amount at step 1216. For example, a 10.0 ms battery current may be measured and evaluated to see if the absolute value of the current is greater than 1A current. If the battery current exceeds the predetermined amount, process 1200 again proceeds to step 1224, where the BMS issues a soft fault indicating that there may be an auxiliary contactor and/or an auxiliary voltage sense fault. Conversely, if the current measured in step 1214 is below the predetermined amount, the process 1200 continues to step 1218, where the main contactor is turned on and the battery pack current is again measured for a predetermined period of time. After step 1218, process 1200 may continue to step 1220, which corresponds to the beginning of process 1300.

Referring to fig. 13, an automated process 1300 for determining the ability of a battery pack to engage in parallel with other battery packs using bleed circuit discharge is illustrated. Process 1300 begins at step 1302, BMS 1118 determines whether the current exceeds a predetermined amount. For example, the battery current may have a predetermined limit of 1A. Therefore, BMS 1118 needs to verify that the absolute value of the current is not greater than 1A current. If the BMS 1118 detects that the battery pack current exceeds the predetermined amount, the process 1300 proceeds to step 1318 and the BMS 1118 issues a soft fault indicating that there may be a bleed circuit 608 fault. If the current measured in step 1302 is below the predetermined amount, process 1300 proceeds to step 1304 and delays the time by a predetermined amount of time determined by a discharge sorting table (e.g., discharge sorting table 1000). The predetermined amount of time may be based on a voltage of the battery pack. Once the predetermined time period has elapsed, the BMS 1118 may turn on the bleed circuit and measure the percent change in the terminal bus voltage (i.e., the main voltage sense potential) in step 1306. If the percentage change in the terminal bus voltage after operating the bleed circuitry 608, as determined by the BMS 1118 at step 1308, is greater than a predetermined value, the BMS 1118 may prompt the battery pack to engage the terminal bus by engaging the auxiliary contactors and changing the mode of the battery pack to "discharge" at step 1310.

In some embodiments, if the percentage change is greater than 15% within 100 ms, the auxiliary contactor 1102 turns on and the battery pack 600 engages the positive terminal bus 122 and enters a "discharge" mode.

However, if at step 1308 it is found that the percentage change is below a predetermined value, process 1300 proceeds to step 1312, where BMS 1118 causes the bleeding circuit to continue operating for an additional predetermined time. In some embodiments, the predetermined value is 15% within 100 ms, and the additional predetermined time for which the bleeding circuit operation continues is 50 ms, giving a total amount of time of 150 ms. At step 1314, the BMS 1118 determines whether the percentage change is now greater than a predetermined value. If it is determined after the additional bleed circuitry operation at

steps

1312 and 1314 that the percentage change is sufficiently high, the process 1300 proceeds to step 1310, where the BMS 1118 causes the auxiliary contactor 1102 to engage the terminal bus (e.g., the positive terminal bus 122) and change the mode to "discharge" at step 1310. However, if the percentage change is too low even after the increased operating time of the bleed circuit, the process 1300 proceeds to step 1316 by changing the mode of the battery pack to "stand-by discharge" in the communication mode. In some embodiments, the goal of parallel connection during discharge mode is to have all battery packs engage the positive terminal bus within 3 seconds. In summary, in the discharge mode, the batteries come onto a common positive terminal bus (e.g., positive terminal bus 122) using timing based on individual battery pack voltages, and then attempt to bleed off the voltage of the terminal bus. If the battery can bleed off the voltage, the battery may engage, but if the bleed off circuit does not bleed off the voltage, the battery may determine whether engagement is safe. The battery may engage the parallel configuration if the battery has determined that the engagement is safe. Otherwise, if the bond is not safe, the battery may wait for the bond and continue to monitor the voltage on the terminal bus until the bond is safe. This may be determined using some or all of the same steps as in

processes

1200 and 1300, repeating until the battery is found to be able to safely engage after successfully bleeding the voltage of the terminal bus.

Referring to fig. 14, an example of a bleed circuit timeline sequence for discharging one of the battery packs in the battery system of fig. 1 is shown, according to an exemplary embodiment. All battery packs (e.g., battery packs 102, 104, 106, 108) receive the same discharge enable signal at the same time. In accordance with the discharge sequencing table 1000, as described with reference to fig. 10, the 58.1V first battery pack 1418 has a specified delay time of 200 ms before beginning a bleed down test using its bleed down circuit (e.g., bleed down circuit 608), with delay 1402 shown in gray. Because the battery packs 1420, 1422 have measured voltages of 56.8V to 57.8V, the battery pack 1420 and battery pack 1422 have a specified delay 1402 of 450 ms. The battery pack 1424 has a 700 ms delay 1402 before beginning its bleed-off test. Battery pack 1418, battery pack 1420, battery pack 1422, and battery pack 1424 each attempt to engage a battery system, such as battery system 100, in a parallel configuration. In some embodiments, the timeline ordering of the bleeding circuit 608 has the following order: delay 1402, measure main (terminal) voltage 1404, measure auxiliary voltage 1406, test auxiliary contactor 1408, turn on primary contactor (and dwell time) 1410, bleed off test a part 1412, bleed off test B part 1414, and agree to engage decision 1416. In other embodiments, the bleed off test B part 1414 is not necessary until the battery pack receives an agreement to engage decision. The bleed down test part a may be 100 ms for each battery pack, while the bleed down test part B may be an increased 50 ms for each battery pack. Only machines with particularly large capacitances may need to bleed off test B section 1414, requiring extended test times. Battery pack 1418, battery pack 1420, and battery pack 1422 may all engage the terminal bus after "agree to engage decision" 1416 because their respective measured terminal voltages (which may be measured in step 1204 of process 1200) are within the engagement voltage, such as 1.00V for another battery pack on the terminal bus. However, the battery pack 1424 has an exemplary terminal voltage of 56.0V and is outside of the junction voltage. Thus, the battery pack 1424 waits in a "standby" mode to engage when the battery pack becomes safe (e.g., the SOC of the other battery packs 1418, 1420, 1422 has dropped into the 1.00V range).

Referring to fig. 15, a parallel example 1500 of a bleed circuit sequence of a parallel process for discharging a battery pack (such as battery pack 1100) to engage battery system 100 is shown, according to an example embodiment. In the parallel example 1500, there is only one battery pack (i.e., not parallel), and the system does not have a terminal energy storage device, such as a capacitor or another battery pack. At time 1502, a battery management system (e.g., BMS 1118) receives a discharge enable signal. At 1504, the BMS 1118 waits for a predetermined amount of time based on the battery pack voltage 1510 according to the discharge sequencing table 1000. After a predetermined amount of time from when the discharge enable signal was received at time 1502, at time 1506, the BMS 1118 turns on its bleeder circuit to test whether a terminal energy storage device is present on the terminal bus. Then, at time 1508, if BMS 1118 finds it safe, BMS 1118 turns on all of the contacts (e.g., secondary contacts 1102 and primary contacts 1104) to engage the terminals. In parallel example 1500, safety is determined (i.e., engagement is agreed) because there is no terminal voltage at time 1508, meaning there is no other capacitor or battery on the terminals.

Referring to fig. 16, a parallel example 1600 of a bleed circuit sequence of a parallel process for discharging a battery pack (such as battery pack 1100) to engage battery system 100 is shown, according to an example embodiment. In the parallel example 1600, there is only one battery pack (i.e., not parallel), and the system (e.g., equipment coupled to the terminal bus) has a terminal energy storage device, such as a capacitor or another battery pack. At time 1602, a battery management system (e.g., BMS 1118) receives a discharge enable signal. At 1604, the BMS 1118 waits for a predetermined amount of time based on the battery pack voltage 1610 according to the discharge sequencing table 1000. Once the predetermined delay from when the discharge enable signal is received at time 1602 ends, at time 1606, the BMS 1118 turns on its bleed off circuit to test for the presence of a terminal energy storage device (such as a battery pack or capacitor). Next, at time 1608, if BMS 1118 determines that it is safe, BMS 1118 turns on all of the contactors (e.g., auxiliary contactor 1102 and main contactor 1104) to engage the terminals (e.g., positive terminal bus 122). In the parallel example 1600, it is considered safe (i.e., agreeing to engage) because the bleed circuit is able to bleed the terminal voltage 1612, meaning that the connected terminal energy storage device is a capacitor rather than a battery.

Referring to fig. 17, a parallel example 1700 of a bleed circuit sequence for a parallel process for discharging a battery pack (such as battery pack 1100) to engage battery system 100 is shown, according to an exemplary embodiment. In the parallel example 1700, there is only one battery pack (i.e., not parallel) and the system has a terminal energy storage device. At time 1702, a battery management system (e.g., BMS 1118) receives a discharge enable signal. At 1704, the BMS 1118 waits for a delay period based on the battery voltage 1710 according to the discharge ranking table 1000. After the predetermined delay has elapsed, at time 1706 BMS 1118 turns on its bleed circuit to test the terminal energy storage device connection to the terminal bus. Then, at time 1708, if BMS 1118 finds it safe, BMS 1118 turns on all of the contacts (e.g., secondary contact 1102 and primary contact 1104) to engage the terminal bus. It is determined to be safe (i.e., agree to engage) in the parallel example 1700 even though the bleed circuit is unable to bleed the terminal voltage (indicating the presence of another battery pack). Because the voltage of the battery pack 1100 is within the terminal blocking voltage, the engagement of the battery pack 1100 is safe. For example, when BMS 1118 turns on all contactors to engage the terminal bus, battery pack voltage 1710 is 57.2V and terminal voltage 1712 is 57.8V.

Referring to fig. 18, a parallel example 1800 of a bleed circuit sequence for a parallel process of engaging the battery system 100 to discharge is shown according to an example embodiment. In the parallel example 1800, there are two battery packs, with no CANbus network communication. At time 1802, each BMS of the two battery packs receives a discharge enable signal. At time 1804, each BMS waits a predetermined amount of time according to the discharge sequencing table 1000 based on the battery pack voltage 1814 of the first battery pack and based on the battery pack voltage 1816 of the second battery pack. Because the

cell stack voltages

1814, 1816 are different, each cell stack has its own respective delay. After the delay for the first battery pack ends, the first BMS turns on a bleeder circuit for the first battery pack to test the terminal energy storage device at 1806. At time 1808, if the first BMS finds it safe, it turns on all of the contactors (e.g., the auxiliary contactor 1102 and the main contactor 1104) to engage the terminals.

In the parallel example 1800, it is determined that the first battery pack is engaged (i.e., engagement is granted) because there is no terminal voltage at time 1808, which means that the battery pack is first engaged with the terminal bus. At time 1810, the delay for the second battery pack ends, and the second BMS turns on the bleed off circuit of the second battery pack to test the terminal energy storage device. Then at time 1812, if the second BMS determines that its engagement is safe, it turns on all the contactors of the second battery pack to engage the terminals. Engagement of the second battery pack is also found to be safe because the battery pack voltage 1816 is within the terminal blocking voltage despite the absence of bleeding terminal voltage. The terminal voltage will then be adjusted based on the

battery pack voltages

1814, 1816 1818.

Referring to fig. 19, a parallel example 1900 of a bleed circuit sequence for a parallel process of two battery pack engaged battery systems 100 to discharge is shown according to an exemplary embodiment. In the parallel example 1900, there are two battery packs without CANbus network communication, but in other embodiments there may be more than two battery packs. At time 1902, each BMS of the two battery packs receives a discharge enable signal. At time 1904, based on the battery voltage 1914 of the first battery pack and based on the battery voltage 1916 of the second battery pack, each BMS waits a predetermined amount of time according to the discharge sequencing table 1000, each battery pack having their own respective delay. Once the delay for the first battery pack ends, the first BMS turns on a bleeder circuit for the first battery pack to test the terminal energy storage device at 1906. At time 1908, if the first BMS finds it safe, it turns on all of the contactors (e.g., the secondary contactor 1102 and the primary contactor 1104) to engage the terminal bus.

In the parallel example 1900, it is determined that the first battery pack is engaged (i.e., engagement is granted) because there is no terminal voltage at time 1908, which means that the battery pack is the first to engage the terminal bus. At time 1910, the delay for the second battery pack ends and the second BMS turns on the bleed off circuit of the second battery pack to test the terminal energy storage device. At time 1912, if the second BMS determines that its engagement is safe, it turns on all contactors of the second battery pack to engage the terminals. The engagement of the second battery pack is found to be unsafe because the bleed circuit of the second battery pack cannot bleed the terminal voltage, and the battery pack voltage 1916 is outside of the terminal blocking voltage. For example, the blocking voltage is +/-1.00V, the terminal voltage 1918 is 57.5V and the battery voltage 1916 of the second battery pack is 55.1V, meaning that the second battery pack is not within the blocking range of the terminals. The second battery pack will continue to monitor (e.g., periodically or continuously) the voltage on the terminal bus and will remain in standby mode until the voltage on the terminal bus falls within the lockout voltage range so that the second battery pack can then safely engage the terminal bus.

Referring to fig. 20, a charge sequencing table 2000 is shown that may be used in a parallel process for battery system 100, such as process 2100 described with reference to fig. 21. The charging sequencing table 1000 may include a delay column 2002, a voltage range column 2004, and a sequence number column 2006. The voltage range column 2004 may be used in the process 2100 as described with reference to fig. 21 to find the delay (in ms) corresponding to the measured terminal bus voltage value during step 2110. For the charge sequencing Table 2000, the standard blocking voltage is set to +/-1.00V, and the next sequential incremental delay time is increased by 250 ms. In some embodiments, active CANbus communication between BMS within each battery pack to the charger is required in order to charge any battery pack. In some examples, the BMS may not allow battery pack charging if the BMS does not have a CANbus communication network that is operating properly.

Referring to fig. 21, a flow diagram of an automated process 2100 for determining the ability of a battery pack to engage in parallel with other battery packs using bleed circuit charging is shown. Process 2100 begins by performing a CAN source address request process to determine if there are other batteries on the CAN bus network. Step 2102 may occur a predetermined time (such as 1.5 seconds) from the charge enable signal input, which should be the exact same amount of time, regardless of whether another battery is found to be present. The presence or absence of any other CAN-enabled battery is recorded and potentially performed by the battery system (e.g., battery system 100). Process 2100 proceeds to step 2104, where the battery pack determines whether there is another battery on CANbus, which determination may be performed by a BMS (such as BMS 714). If another battery is found to be present at step 2104, process 2100 includes waiting a predetermined amount of time at step 2118 and then proceeding to step 2106. For example, if there is another battery but it is not connected via CAN, during the waiting period, the other battery will time out and then the CAN-enabled battery is allowed to start charging.

Conversely, if there is no other battery on the CANbus, process 2100 immediately proceeds to step 2106. At step 2106, the main contactor (e.g., main contactor 702) voltage sensing potential, which is also the terminal bus voltage, is measured. At step 2108, BMS 714 determines whether the measured voltage is greater than or less than a predetermined value. If the voltage is found to be greater than the predetermined value in step 2108, BMS 714 issues a soft fault and may require a charge enable reset cycle at step 2116. For example, if the predetermined value is 60V and the measured value is greater than 60V, BMS 714 may issue a soft fault indicating that a "high terminal bus voltage" is present.

However, if the voltage is found to be less than the predetermined value in step 2108, process 2100 proceeds to step 2110 where BMS 714 delays the time based on the measured battery voltage according to a charging schedule (e.g., charging schedule 2000). After the delay time from step 2110, the process 2100 continues by turning on the bleed down circuit (e.g., the bleed down circuit 608) and measuring the percentage change in the terminal bus voltage at step 2112. Once the change in terminal bus voltage is measured, process 2100 proceeds to step 2114, which begins process 2200 shown in fig. 22.

Referring to fig. 22, a flow diagram of an automated process 2200 for determining the ability of a battery pack to engage in parallel with other battery packs using bleeder circuit charging is shown, according to an exemplary embodiment. As described above, process 2200 begins at the end of process 2100. In some embodiments, process 2200 begins at step 2202 with BMS 714 determining whether the percentage change in the terminal bus voltage after the voltage turns on bleeder circuit 608 in step 2112 of process 2100 is greater than a predetermined value. If the percentage change is found to be greater than the predetermined value, process 2200 proceeds to step 2204 where the battery pack engages the terminal bus (by turning on the main contactors) and changes its mode to "charging". For example, if the percentage change is greater than 15% after 100 ms, the main contactor 702 is turned on and the battery pack 600 engages the positive terminal bus 122 and enters a "charging" mode. In some embodiments, a charger timeout countdown for 10 seconds begins after entering the "charge" mode, and if no charger is present, a soft fault is issued and a charge enable period is required.

If the percentage change is found to be less than the predetermined value in step 2202, process 2200 proceeds to step 2206 where BMS 714 continues bleed circuit operation for an additional predetermined time. In some embodiments, by the end of 100 ms, the predetermined value is 15%, and the additional predetermined time for which the bleeding circuit operation continues is 50 ms, giving a total of 150 ms. Once the additional predetermined time of bleeder circuit operation has expired, BMS 714 may again determine whether the percentage change is now greater than the predetermined value at step 2208. If after this additional time, the percentage change is now large enough, process 2200 proceeds to step 2204 where the battery pack engages the terminal bus and transitions to a "charging" mode. If the percentage change is still not large enough after step 2208, process 2200 proceeds to step 2210 where BMS 714 continues to determine if there are additional batteries on the CANbus. Process 2200 includes changing the mode to "stand-by discharge" in communication mode at step 2212, and then following a charging sequence to engage the terminal bus once the battery pack is within the blocking voltage of any other battery pack on CANbus (i.e., there are 2 or more battery packs) at step 2214. If there are no other battery packs (i.e., there are only battery packs attempting to engage), process 2200 includes changing the mode to "communication" mode at step 2216, and then issuing a soft fault (e.g., a soft fault requiring a charge enable cycle) at step 2218. In some embodiments, it is desirable to restart the charging cycle to prevent the battery pack from attempting to charge blindly without sending a CAN message to the charger.

Referring to fig. 23, an automatic process 2300 for determining the ability of a battery pack to be engaged in parallel with other battery packs using bleeder circuit charging is shown, according to an exemplary embodiment. Process 2300 begins with step 2302 in which a battery pack performs a CAN source address request process to determine if there are other batteries on a CANbus network. Step 2302 may occur a predetermined time (e.g., 1.5 seconds) from the charge enable signal input, which may be selected to be the same in amount of time regardless of whether any other batteries are found to be present. The presence or absence of any other CAN-enabled battery is recorded. Process 2300 then includes determining whether there is another battery on the CANbus at step 2304, which may be performed by a BMS (such as BMS 1118) of the battery pack 600. If at step 2304 the BMS 1118 finds that another battery is present, the process 2300 includes waiting for a predetermined amount of time at step 2322 and then proceeds to step 2306. For example, if there is another battery but it is not connected via CAN, during the wait period, the other battery will time out and then allow the CAN-enabled battery to charge.

Instead, if there is no other battery on the CANbus, process 2300 immediately proceeds to step 2306. At step 2306, process 2300 includes measuring a main contactor (e.g., main contactor 1104) voltage sensing potential (i.e., terminal bus voltage). In some embodiments, at step 2308, BMS 1118 takes a measurement and then determines whether the measured voltage is greater than or less than a predetermined value. If the voltage is found to be greater than the predetermined value in step 2308, process 2300 continues to step 2320 and a soft fault is issued and a charge enable reset cycle is required. For example, if the predetermined value is 60V and the measured value is greater than 60V, the process 2300 (e.g., with BMS 1118) may issue a soft fault indicating that a "high terminal bus voltage" is present, and then a charge enable reset cycle of the battery pack may be required. However, if BMS 1118 finds that the voltage is less than the predetermined value in step 2308, process 2300 continues to step 2310 and includes measuring the secondary (contactor) voltage sensing potential. At step 2312, the process includes checking if the measured auxiliary voltage is zero, which may indicate a problem with the main contactor or a fault with BMS 1118. If the auxiliary voltage is not 0V, a soft fault is issued at step 2318 indicating that there may be a main contactor or BMS fault. However, if the secondary voltage is 0V, process 2300 proceeds to step 2314, where a bleed circuit (e.g., bleed circuit 608) is turned on and the current of the battery pack is measured for a predetermined period of time. The process ends at step 2316 and proceeds to process 2400 shown in fig. 24.

Referring to fig. 24, an automatic process 2400 for determining the ability of a battery pack to engage in parallel with other battery packs using bleeder circuit charging is shown, according to an exemplary embodiment. Once the battery current is measured in step 2314 of the process 2300, the BMS 1118 determines whether the current exceeds a predetermined amount at step 2402. For example, a 10.0 ms battery current may be measured and the current checked to see if the absolute value of the current is greater than 1A current. If the battery pack current exceeds the predetermined amount, process 2400 proceeds to step 2424 where BMS 1118 issues a soft fault indicating that there may be an auxiliary contactor and/or an auxiliary voltage sense fault. If the current measured in step 2314 is less than the predetermined amount, process 2400 proceeds to step 2404 where BMS 1118 turns on the main contactor and again measures the battery current for a predetermined period of time.

At step 2406, the BMS 1118 may determine whether the current measured in step 2404 exceeds a predetermined amount. For example, the battery current may have a limit of 1A. Therefore, BMS 1118 needs to verify that the absolute value of the current exceeds a current greater than 1A. The process 2400 includes: at step 2422, if the battery pack current exceeds the predetermined amount, a soft fault is issued indicating that a bleed circuit 608 fault may have occurred. If the measured current is less than the predetermined amount in step 2406, process 2400 proceeds to step 2408 and includes delaying a time based on the measured voltage according to a charging schedule (e.g., charging schedule 2000). At step 2410, process 2400 includes engaging the bleed circuit and measuring a percentage change in the terminal bus voltage (i.e., the primary voltage sense potential).

At step 2412, process 2400 includes determining whether the percent change in the terminal bus voltage after operating bleed circuit 608 is greater than a predetermined value, which can be performed by BMS 1118. If the percentage change is greater, process 2400 proceeds to step 2414 by engaging the terminal bus (by turning on the secondary contactor) and changing the mode to "charging". In some embodiments, if the percentage change is greater than 15% within 100 ms, the auxiliary contactor 1102 turns on and the battery pack 600 engages the positive terminal bus 122 and enters a "charging" mode.

Still referring to fig. 24, conversely, if the percentage change is found to be below the predetermined value in step 2412, process 2400 proceeds to step 2416 and continues the bleeding circuit operation for an additional predetermined time. In some embodiments, the predetermined value is 15% within 100 ms, and the additional predetermined time for which the bleeding circuit operation continues is 50 ms, giving a total time value of 150 ms. At step 2418, process 2400 includes determining whether the percentage change is greater than a predetermined value after the additional time. If the percentage change is sufficiently large after the additional bleeder circuit operation, the process 2400 proceeds to step 2414 by engaging the terminal bus (e.g., the positive terminal bus 122) and changing the mode to "charge". Conversely, if the percentage change is still too low after the increased time to operate the bleed circuitry, process 2400 includes changing the battery mode to "standby charging" in the communication mode at step 2420.

In some embodiments, the goal of the parallel system in the charging mode is to rebalance all battery packs in the parallel configuration (e.g., battery pack 402, battery pack 404, battery pack 406, and battery pack 408 as described with reference to fig. 4). In summary, during a charging mode for parallel engagement, a battery (e.g., battery pack 402) may begin its positive terminal bus sequence with opposite timing based on the individual voltages of the battery pack 402. According to an exemplary embodiment, after checking whether there is a terminal bus voltage, if there is no terminal bus voltage, the battery pack will engage, and if there is a terminal bus voltage, it will attempt to bleed the circuit. The battery pack may then engage the parallel system if the circuit does bleed, and an alarm may be generated if the circuit does not bleed. All batteries in charge mode may issue a Constant Current (CC) command until any one of the batteries issues a Constant Voltage (CV) command. Once one battery issues a CV command, all other batteries may also enter CV mode. In some embodiments, the CV command is from the weakest cell in the parallel cell system. This may occur because the battery may negotiate to suspend or terminate charging, or later revert to a "top-of-charge" battery that performs better in the system. In the battery system, any one battery can command the charger. Further, an initial low charge rate may be requested that is used to determine how many chargers are present on the bus. Two or more measurements may be made and then the updated charge rate may be used with a multiplier. There may be a command string sent by the digital communication protocol to accurately assess how many chargers are connected to the parallel system.

The various methods and systems described herein may allow battery systems in various types of equipment (e.g., outdoor power equipment, indoor power equipment, portable field equipment, military vehicle applications, etc.) to safely utilize parallel battery packs and prevent damage to the health of the battery packs when they attempt to engage the system in a parallel configuration. Timed entry of the parallel configuration to close the bleed circuit and engage other battery packs (as described in

processes

1200, 1300, 2100, 2200, etc.) may advantageously allow the battery packs to avoid current inrush that is detrimental to the functionality of the battery packs. Delays in the sequencing table may also become more useful as the battery pack ages. In addition, having dual-axis contactors prevents physical impact in one direction (e.g., axial to the contactor) from causing both the primary and secondary contactors to close due to the same impact load. The charging capability of the method described with reference to fig. 21-24 may help to rebalance all battery packs having unique states of charge in a parallel configuration. When the internal resistance in the stack is also low, the parallel configuration with an unbalanced stack can lead to a destructive condition, such as instantaneous 2000 amps of current from one stack to another. By preventing damaging transient currents in the battery packs of the system, the battery life of the battery system in different types of equipment may be extended.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular implementations. Certain features that are described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Furthermore, although certain features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

It should be understood that although the use of words such as "desired" or "appropriate" used in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, that scope being defined by the claims that follow. In reading the claims, when words such as "a," "an," or "at least one" are used, it is not intended that the claims be limited to only one item unless specifically stated to the contrary in the claims.

It should be noted that certain paragraphs of the disclosure may refer to terms such as "first" and "second" in connection with sides, ends, etc. to identify or distinguish one from another or from another. These terms are not intended to relate the entities (e.g., first side and second side) only in time or according to an order, although in some cases, the entities may include such relationships. Nor are these terms limiting the number of possible entities (e.g., sides or ends) that may operate within a system or environment.

The terms "coupled" and "connected," and the like, as used herein, mean that two components are directly or indirectly joined to each other. Such engagement may be fixed (e.g., permanent) or movable (e.g., detachable or releasable). Such joining may be achieved with the two components or the two components and any additional intermediate components being integrally formed as a single unitary body with one another or with the two components or the two components and any additional intermediate components being attached to one another.

As used herein, the term "circuitry" may include hardware configured to perform the functions described herein. In some embodiments, each respective "circuit" may include a machine-readable medium for configuring hardware to perform the functions described herein. The circuitry may be embodied as one or more circuit components including, but not limited to, processing circuitry, network interfaces, peripherals, input devices, output devices, sensors, and the like. In some embodiments, the circuitry may take the form of one or more analog circuits, electronic circuits (e.g., Integrated Circuits (ICs), discrete circuits, system-on-a-chip (SOC) circuits, etc.), telecommunications circuits, hybrid circuits, and any other type of "circuit. In this regard, "circuitry" may include any type of component for implementing or facilitating implementation of the operations described herein. For example, a circuit as described herein may include one OR more transistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR, etc.), resistors, multiplexers, registers, capacitors, inductors, diodes, wiring, etc.

"circuitry" may also include one or more processors communicatively coupled to one or more memories or memory devices. In this regard, the one or more processors may execute instructions stored in the memory or may execute instructions otherwise accessible to the one or more processors. In some embodiments, the one or more processors may be embodied in various ways. The one or more processors may be constructed in a manner sufficient to perform at least the operations described herein. In some embodiments, the one or more processors may be shared by multiple circuits (e.g., circuit a and circuit B may include or otherwise share the same processor, which in some example embodiments may execute instructions stored or otherwise accessed via different regions of memory). Alternatively or additionally, the one or more processors may be configured to perform or otherwise perform certain operations independently of the one or more coprocessors. In other example embodiments, two or more processors may be coupled via a bus to enable independent, parallel, pipelined, or multithreaded instruction execution. Each processor may be implemented as one or more general-purpose processors, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), or other suitable electronic data processing components configured to execute instructions provided by a memory. The one or more processors may take the form of single-core processors, multi-core processors (e.g., dual-core processors, three-core processors, four-core processors, etc.), microprocessors, and the like. In some embodiments, the one or more processors may be external to the apparatus, e.g., the one or more processors may be remote processors (e.g., cloud-based processors). Alternatively or additionally, the one or more processors may be internal to the device and/or local to the device. In this regard, a given circuit or component thereof may be disposed locally (e.g., as part of a local server, local computing system, etc.) or at a remote location (e.g., as part of a remote server, such as a cloud-based server). To this end, a "circuit" as described herein may include components distributed across one or more locations.

Claims

1. A battery pack, comprising:

a housing having a positive terminal and a negative terminal;

a plurality of battery cells located within the housing and selectively coupled to the positive terminal and to the negative terminal;

a battery management system located within the housing and configured to operate a first switch within the housing to selectively couple the plurality of battery cells and the positive terminal;

a bleed circuit electrically coupled between the positive terminal and the negative terminal, the bleed circuit including a resistor and a second switch for selectively coupling the positive terminal to the negative terminal;

wherein the battery management system is configured to open the first switch and close the second switch, and measure a voltage drop across the resistor to detect the presence and type of a voltage source connected to the positive terminal.

2. The battery pack of claim 1, wherein the battery management system measures the voltage drop across the resistor by comparing a first measured voltage to a second measured voltage, the second measured voltage measured at a time interval after the first measured voltage.

3. The battery pack of claim 2, wherein the battery management system detects the type of the voltage source connected to the positive terminal by comparing the first measured voltage to the second measured voltage and determining whether a difference between the first measured voltage and the second measured voltage exceeds a threshold.

4. The battery pack of claim 3, wherein the battery management system determines that the voltage source is capacitive if the difference between the first measured voltage and the second measured voltage exceeds the threshold.

5. The battery pack of claim 3, wherein the battery management system determines that the voltage source is a battery if the difference between the first measured voltage and the second measured voltage does not exceed the threshold.

6. The battery pack of claim 3, wherein the battery management system is configured to open the second switch and close the first switch to couple the battery cell to the positive terminal and decouple the bleed circuit from the positive terminal in response to determining that the difference between the first measured voltage and the second measured voltage exceeds the threshold.

7. The battery pack of claim 1, further comprising a third switch within the housing and in communication with the battery management system, the third switch positioned in series with the first switch and the positive terminal and positioned in series with the bleed circuit, wherein the bleed circuit is decoupled from the positive terminal when the third switch is open, and wherein at least a portion of the bleed circuit is coupled with the positive terminal when the third switch is closed.

8. The battery pack of claim 7, wherein the battery management system senses a voltage source connected to the positive terminal by comparing voltage signals upstream of the third switch and downstream of the third switch when the third switch is open and the second switch is closed.

9. The battery pack of claim 7, wherein after the battery management system detects that the voltage source is connected to the positive terminal, the battery management system is configured to close the third switch to electrically couple the bleed circuit to the positive terminal to detect a type of the voltage source connected to the positive terminal, the type of the voltage source determined by comparing a measured voltage drop across the resistor over a period of time and comparing the measured voltage drop to a threshold.

10. The battery pack of claim 9, wherein the battery management system is configured to close the first switch, open the second switch, and close the third switch to couple the battery cell to the positive terminal upon detecting that the voltage source is capacitive.

11. The battery pack of claim 9, wherein the battery management system is configured to close the first switch, open the second switch, and close the third switch to couple the battery cell to the positive terminal upon detecting that the voltage source is a battery having a discharge voltage within a predetermined range.

12. The battery pack of claim 9, wherein the battery management system is configured to keep the first switch open upon detecting that the voltage source is a battery having a discharge voltage outside a predetermined range.

13. The battery pack of claim 1, wherein the battery management system is coupled to a controller area network bus (CANbus) link configured to communicate a state of charge of the battery pack with an additional battery pack.

14. A battery pack, comprising:

A housing including a positive terminal and a negative terminal;

a plurality of battery cells housed within the housing and selectively coupled to the positive terminal and to the negative terminal;

a battery management system housed within the enclosure and configured to operate a primary contactor switch and a secondary contactor switch to selectively couple the plurality of battery cells and the positive terminal;

a bleed circuit extending between the positive terminal and the negative terminal, the bleed circuit including a resistor and a bleed switch for selectively coupling the positive terminal to the negative terminal;

wherein the battery management system is configured to determine the presence of a voltage source on the positive terminal when the auxiliary contactor switch is in an open position;

wherein the battery management system is configured to determine a type of the voltage source on the positive terminal when the auxiliary contactor switch is in a closed position and the bleed switch is in a closed position.

15. The battery pack of claim 14, wherein the battery management system determines the type of the voltage source on the positive terminal when the main contactor switch is in an open position such that the battery cell is decoupled from the positive terminal.

16. The battery pack of claim 14, wherein the battery management system is configured to open the bleed switch, close the main contactor switch, and close the auxiliary contactor to couple the battery cell to the positive terminal upon determining that a voltage source is not present on the positive terminal.

17. The battery pack of claim 16, wherein the battery management system is configured to open the bleed-off switch, close the main contactor switch, and close the auxiliary contactor switch to couple the battery cell to the positive terminal upon determining that a capacitive voltage source is present on the positive terminal.

18. The battery pack of claim 17, wherein the battery management system is configured to open the bleed off switch, close the main contactor switch, and close the auxiliary contactor switch upon determining that a battery voltage source is present on the positive terminal and that the battery voltage source is providing a voltage within a predetermined voltage range stored within the battery management system.

19. The battery pack of claim 18, wherein the battery management system is configured to keep at least one of the main contactor switch and the auxiliary contactor switch open upon determining that a battery voltage source is present on the positive terminal and that the battery voltage source is providing a voltage outside a predetermined voltage range stored within the battery management system.

20. The battery pack of claim 19, wherein the predetermined voltage range stored within the battery management system is based in part on a detected output voltage of the battery cells within the battery pack as determined by the battery management system.

21. The battery pack of claim 20, wherein the predetermined voltage range is 1.00V.

22. The battery pack of claim 14, wherein the battery management system is configured to discharge electricity from the battery cells to the positive terminal when the main contactor switch and the auxiliary contactor switch are closed.

23. The battery pack of claim 14, wherein the battery management system is coupled to a controller area network bus (CANbus) link configured to communicate a state of charge of the battery pack with an additional battery pack.

24. The battery pack of claim 14, wherein the battery management system is configured to determine the type of the voltage source on the positive terminal by comparing a percentage change in measured voltage across the bleed circuit over a period of time.

25. The battery pack of claim 24, wherein the battery management system determines that the type of the voltage source on the positive terminal is capacitive if the percentage change in measured voltage on the bleed off circuit over the period of time exceeds a threshold percentage.

26. The battery pack of claim 25, wherein the battery management system determines that the type of the voltage source on the positive terminal is a battery if the percentage change in measured voltage across the bleed down circuit does not exceed the threshold percentage over the period of time.

27. The battery pack of claim 26, wherein the battery management system is configured to close the main contactor switch and the auxiliary contactor switch in response to detecting that the voltage source is providing a voltage to the positive terminal that is within a predetermined limit, the predetermined limit corresponding to a difference from a voltage sourced by the battery cells.

28. The battery pack of claim 27, wherein the battery management system is configured to open at least one of the main contactor switch and the auxiliary contactor switch in response to detecting that the voltage source is providing a voltage to the positive terminal that is outside the predetermined limit.

29. The battery pack of claim 14, wherein the battery management system is configured to close the main contactor switch and close the auxiliary contactor switch to couple the battery cell to the positive terminal when the detected voltage source is capacitive or battery based.

30. The battery pack of claim 29, wherein the battery management system is configured to maintain at least one of the main contactor switch and the auxiliary contactor switch in the open position to prevent the battery cell from being coupled to the positive terminal if a battery-based voltage source outside a predetermined voltage range is detected on the positive terminal.

31. The battery pack of claim 14, wherein the positive terminal is coupled to a positive terminal bus comprising at least one additional battery pack.

32. The battery pack of claim 14, wherein the positive terminal is coupled to a positive terminal bus on a power equipment.

33. The battery pack of claim 14, wherein the battery management system is configured to determine the type of the voltage source on the positive terminal by measuring a percentage change in voltage across the bleed circuit over a period of about 100 milliseconds.

34. The battery pack of claim 33, wherein the battery management system is configured to determine the type of the voltage source on the positive terminal by comparing a percentage change in the voltage across the bleed circuit to a threshold of about fifteen percent.

35. A battery system, the battery system comprising:

a first battery pack coupled to a terminal bus and providing a voltage to the terminal bus;

a second battery pack coupled to the terminal bus, the second battery pack comprising:

a positive terminal and a negative terminal,

a bleed circuit selectively coupled to the negative terminal,

one or more of the plurality of contactors is,

one or more battery cells selectively coupled to the positive terminal and selectively coupled to the terminal bus based on a position of the one or more contactors, an

A battery management system configured to:

measuring the voltage of the terminal bus coupled to the bleed circuit, the voltage corresponding to an output voltage of the first battery pack;

determining whether the voltage of the terminal bus is less than a predetermined value;

in response to determining that the voltage is less than the predetermined value, turning on the bleeding circuit with the terminal bus to attempt to bleed the voltage of the terminal bus;

in response to determining that the voltage of the terminal bus is not bleeding by a predetermined threshold amount, determining whether the voltage of the terminal bus is within a lockout voltage range; and

Coupling the battery cell to the terminal bus by closing the one or more contactors in response to determining that the voltage of the terminal bus is within the lockout voltage range.

36. The battery system of claim 35, wherein the battery management system is configured to change a mode of the second battery pack to communicate with a digital communication protocol to couple the second battery pack to the first battery pack.

37. The battery system of claim 36, wherein the battery management system is configured to determine the presence of other battery packs connected to the digital communication protocol by performing a source address request procedure.

38. The battery system of claim 35, wherein the bleed circuit of the second battery pack comprises a pre-charge relay positioned in series with the battery cell, a bleed switch of the bleed circuit, and the negative terminal.

39. A battery system, the battery system comprising:

a plurality of battery packs in a parallel configuration;

a standalone battery pack comprising a bleed circuit, a primary contactor, a secondary contactor, one or more battery cells, and a battery management system configured to:

Measuring a voltage of a terminal bus coupled to the bleeding circuit;

measuring a voltage between the main contactor and the auxiliary contactor;

delaying initiation of a test coupling the individual battery packs to the plurality of battery packs based on a preprogrammed value;

turning on the bleed circuit of the individual battery pack to attempt to bleed the voltage of the terminal bus; and

coupling the independent battery pack to the plurality of battery packs in response to the voltage of the terminal bus bleeding by a threshold amount.

40. The battery system of claim 39, wherein coupling the individual battery packs with the plurality of battery packs comprises turning on the primary contactors and turning on the secondary contactors of the individual battery packs.

41. The battery system of claim 9, wherein the battery management system is further configured to change a mode of the standalone battery pack to communicate with a digital communication protocol to couple to the plurality of battery packs once the bleed circuit bleeds the voltage of the terminal bus indicating that it is safe to couple the standalone battery pack to the plurality of battery packs.

42. The battery system of claim 41, wherein the battery management system is further configured to determine the presence of other battery packs connected to the digital communication protocol by performing a source address request procedure.

43. The battery system of claim 42, wherein the battery system is in a discharged state.

44. A method, the method comprising:

measuring a voltage of a terminal bus coupled to a bleed off circuit of an individual battery pack, wherein the individual battery pack includes the bleed off circuit, one or more contactors, one or more battery cell assemblies, and a battery management system;

delaying a start of a test coupling the individual battery packs to a plurality of battery packs based on a predetermined value, wherein the plurality of battery packs are in a parallel configuration;

45. The method of claim 44, wherein the method further comprises changing a mode of the standalone battery pack to communicate with a digital communication protocol to couple to the plurality of battery packs once the bleed circuit bleeds the voltage of the terminal bus, indicating that it is safe to couple the standalone battery pack to the plurality of battery packs.

46. The method of claim 45, wherein the method further comprises determining the presence of other battery packs connected to the digital communication protocol by performing a source address request procedure.

47. The method of claim 46, wherein the plurality of battery packs are in a charged state.

48. The method of claim 44, wherein the one or more contactors include a primary contactor and a secondary contactor.

49. The method of claim 48, wherein coupling the individual battery packs to the plurality of battery packs in the parallel configuration includes turning on the primary contactors and turning on the secondary contactors of the individual battery packs.